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,MOD - R 44X (11 April 1983) <PSL.NMODE-DOC>NM-PROGRAMS.ibm PLA 97_LAS 80 0_FIR 2_INT 1 6.0_TYP 160 163 162 193_INP 12 101_MAR 2 ,END ,PRO 201 OUT 160_202 OUT 163_203 OUT 162_204 OUT 193 205 INP 12 101_206 INP 12 102 ,END ,DEFINE UNIT SPACE FUNCTION ,END 201/NMODE Manual (Editing Programs) Page 20-1 202/20. Editing Programs 201/Special features for editing lisp programs include automatic indentation, parenthesis matching, and the ability to move over and kill balanced expressions. Lisp mode defines paragraphs to be separated only by blank lines and page boundaries. This makes the paragraph commands useful for editing programs. See Section 13.2 [Paragraphs], page 2. Moving over words is useful for editing programs as well as text. See Section 13.1 [Words], page 1. 202/20.1 Major Modes 201/NMODE has many different 202/major modes201/. Two such modes are Text mode and Lisp mode. Each of these customizes NMODE, one for text, the other for Lisp programs. The major modes are mutually exclusive, and one major mode is current at any time. When at top level, NMODE always says in the mode line which major mode you are in. These modes tell NMODE to change the meanings of a few commands to become more specifically adapted to the language being edited. Most commands remain unchanged; the ones which usually change are Tab, Backspace, and Linefeed. In addition, a few special move and mark commands are turned on in Lisp mode which are not available in text mode. Selecting a new major mode can be done with a M-X command. For example M-X Text Mode (203/text-mode-command201/) enters text mode and M-X Lisp Mode (203/lisp-mode-command201/) enters lisp mode. As can be seen from these examples, some major mode's names are the same as the invocations of the functions to select those modes. Often NMODE enters the correct major mode for a file simply based on the file's extension, and you do not have to worry about selecting a mode. Lisp mode specifies that only blank lines separate paragraphs. This is so that the paragraph commands remain useful. 202/20.2 Indentation Commands for Code 201/Tab Indents current line. Linefeed Equivalent to Return followed by Tab. M-^ Joins two lines, leaving one space between if appropriate. C-M-O Split the current line. M-\ Deletes all spaces and tabs around point. M-M Moves to the first nonblank character on the line. Most programming languages have some indentation convention. For Lisp code, lines are indented according to their nesting in parentheses. Whatever the language, to indent a line, use the Tab command. Each major mode defines this command to perform the sort of indentation appropriate for the particular language. In Lisp mode, Tab aligns the line according to its 201/Page 20-2 NMODE Manual (Indentation Commands for Code) depth in parentheses. No matter where in the line you are when you type Tab, it aligns the line as a whole. The command Linefeed (203/indent-new-line-command201/) does a Return and then does a Tab on the next line. Thus, Linefeed at the end of the line makes a following blank line and supplies it with the usual amount of indentation. Linefeed in the middle of a line breaks the line and supplies the usual indentation in front of the new line. The inverse of Linefeed is Meta-^ or C-M-^ (203/delete-indentation-command201/). This command deletes the indentation at the front of the current line, and the line separator as well. They are replaced by a single space, or by no space if before a ")" or after a "(", or at the beginning of a line. With an argument, M-^ joins the current line and the 203/next 201/line, removing indentation at the front of the next line beforehand. To delete just the indentation of a line, go to the beginning of the line and use Meta-\ (203/delete-horizontal-space-command201/), which deletes all spaces and tabs around the cursor. Another command which affects indentation is C-M-O (203/split-line-command201/). It moves the rest of the current line, after point, down vertically. It indents the new line so that the rest of the line winds up in the same column that it was in before the split. If this command is given a positive argument, it adds enough empty lines between the old line and the new line that the total number of lines added equals the argument. The command leaves point unchanged. To insert an indented line before the current one, do C-A, C-O, and then Tab. To make an indented line after the current one, use C-E Linefeed. To move over the indentation on a line, use Meta-M or C-M-M (203/back-to-indentation-command201/). These commands move the cursor forward or back to the first nonblank character on the line. 202/20.3 Automatic Display Of Matching Parentheses 201/The NMODE parenthesis-matching feature is designed to show automatically how parentheses balance in text as it is typed in. When this feature is enabled, after a close parenthesis or other close bracket character is inserted (using 203/insert-closing-bracket201/) the cursor automatically moves for an instant to the open bracket which balances the newly inserted character. The cursor stays at the open parenthesis for a second before returning home, unless you type another command before the second is up. It is worth emphasizing that the location of point, the place where your type-in will be inserted, is not affected by the parenthesis matching feature. It stays after the close parenthesis, where it ought to be. Only the cursor on the screen moves away and back. You can type ahead freely as if the parenthesis display feature did not exist. In fact, if you type fast enough, you won't see the cursor move. You must pause after typing a close parenthesis to let the cursor move to the open parenthesis. 201/NMODE Manual (Automatic Display Of Matching Parentheses) Page 20-3 An additional function is whether NMODE should warn you by ringing the bell if you type an unmatched close parenthesis. NMODE will warn you if you are editing a language in which parentheses are paramount, such as Lisp, but will not do so for languages in which parentheses are not so crucial. 202/20.4 Manipulating Comments 201/M-; Insert comment. M-Z Fill a block of comments. There are two NMODE commands which affect comments. First there is M-; (203/insert-comment-command201/), which jumps to the end of the current line and inserts a percent sign and a space, thus starting a comment. Second, there is M-Z (203/fill-comment-command201/), which allows filling of blocks of comments. It fills a paragraph using whatever text is adjacent to the current line and begins with the same sequence of blank characters, nonalphanumeric characters, and more blank characters as the current line. As a result, it will fill all lines starting with " % ", for instance. Notice that it will NOT do any filling if the current line differs in indentation from the rest of the paragraph of comments (i.e. if it is an indented first line). 202/20.5 Lisp Mode 201/Lisp's simple syntax makes it much easier for an editor to understand; as a result, NMODE can do more for Lisp, and with less work, than for any other language. Lisp programs should be edited in Lisp mode. In this mode, Tab is defined to indent the current line according to the conventions of Lisp programming style. It does not matter where in the line Tab is used; the effect on the line is the same. The function which does the work is called 203/lisp-tab-command201/. Linefeed, as usual, does a Return and a Tab, so it moves to the next line and indents it. As in most modes where indentation is likely to vary from line to line, Backspace (203/delete-backward-hacking-tabs-command 201/in Lisp mode) is redefined to treat a tab as if it were the equivalent number of spaces. This makes it possible to rub out indentation one position at a time without worrying whether it is made up of spaces or tabs. Paragraphs are defined to start only with blank lines so that the paragraph commands can be useful. Auto Fill indents the new lines which it creates. Comments start with "%". 202/20.5.1 Moving Over and Killing Lists and forms 201/C-M-F Move Forward over form. C-M-B Move Backward over form. C-M-K Kill form forward. C-M-Rubout Kill form backward. 201/Page 20-4 NMODE Manual (Moving Over and Killing Lists and forms) C-M-U Move Up and backward in list structure. C-M-( Same as C-M-U. C-( Same as C-M-U. C-M-) Move up and forward in list structure. C-) Same as C-M-). C-M-D Move Down and forward in list structure. C-M-N Move forward over a list. C-M-P Move backward over a list. C-M-T Transpose forms. C-M-@ Put mark after form. M-( Put parentheses around next form(s). M-) Move past next close parenthesis and re-indent. By convention, NMODE commands that deal with balanced parentheses are usually Control-Meta- characters. They tend to be analogous in function to their Control- and Meta- equivalents. These commands are usually thought of as pertaining to Lisp, but can be useful with any language in which some sort of parentheses exist (including English). They are, however, only defined in Lisp mode. To move forward over a form, use C-M-F (203/move-forward-form-command201/). If the first significant character after point is an "(", C-M-F moves past the matching ")". If the first character is a ")", C-M-F just moves past it. If the character begins an atom, C-M-F moves to the end of the atom. C-M-F with an argument repeats that operation the specified number of times; with a negative argument, it moves backward instead. The command C-M-B (203/move-backward-form-command201/) moves backward over a form; it is like C-M-F with the argument's sign reversed. If there are "'"-like characters in front of the form moved over, they are moved over as well. Thus, with point after " 'FOO ", C-M-B leaves point before the "'", not before the "F". These two commands (and the commands in this section) know how to handle comments, string literals, and all other token syntax in (unaltered) PSL. NMODE makes one restriction: it will not handle string literals that extend over multiple lines. Two other commands move over lists instead of forms are often useful. They are C-M-N (203/move-forward-list-command201/) and C-M-P (203/move-backward-list-command201/). They act like C-M-F and C-M-B except that they don't stop on atoms; after moving over an atom, they move over the next expression, stopping after moving over a list. With these commands, you can avoid stopping after all of the atomic arguments to a function. Killing a form at a time can be done with C-M-K (203/kill-forward-form-command201/) and C-M-Rubout (203/kill-backward-form-command201/) commands. C-M-K kills the characters that C-M-F would move over, and C-M-Rubout kills what C-M-B would move over. C-M-F and C-M-B stay at the same level in parentheses, when that's possible. To move 203/up 201/one (or n) levels, use C-M-( or C-M-) (203/backward-up-list 201/and 203/forward-up-list-command201/). C-M-( moves backward up 201/NMODE Manual (Moving Over and Killing Lists and forms) Page 20-5 past one containing "(". C-M-) moves forward up past one containing ")". Given a positive argument, these commands move up the specified number of levels of parentheses. C-M-U is another name for C-M-(, which is easier to type, especially on non-Meta keyboards. If you use that name, it is useful to know that a negative argument makes the command move up forwards, like C-M-). C-M-( and C-M-) are also availible as C-( and C-), respectively, which are easier to type on the hp9836 keyboard. To move 203/down 201/in list structure, use C-M-D (203/down-list-command201/). It is nearly the same as searching for a "(". A somewhat random-sounding command which is nevertheless easy to use is C-M-T (203/transpose-forms201/), which drags the previous form across the next one. An argument serves as a repeat count, and a negative argument drags backwards (thus canceling out the effect of C-M-T with a positive argument). An argument of zero, rather than doing nothing, transposes the forms at the point and the mark. To make the region be the next form in the buffer, use C-M-@ (203/mark-form-command201/) which sets mark at the same place that C-M-F would move to. C-M-@ takes arguments like C-M-F. In particular, a negative argument is useful for putting the mark at the beginning of the previous form. The commands M-( (203/make-parens-command201/) and M-) (203/move-over-paren-command201/) are designed for a style of editing which keeps parentheses balanced at all times. M-( inserts a pair of parentheses, either together as in "()", or, if given an argument, around the next several forms, and leaves point after the open parenthesis. Instead of typing "(FOO)", you can type M-( FOO, which has the same effect except for leaving the cursor before the close parenthesis. Then you type M-), which moves past the close parenthesis, deleting any indentation preceding it (in this example there is none), and indenting with Linefeed after it. 202/20.5.2 Commands for Manipulating Defuns 201/C-M-[, C-M-A Move to beginning of defun. C-M-], C-M-E Move to end of defun. C-M-H Put region around whole defun. For historical reasons, an expression at the top level in the buffer is called a 202/defun201/, regardless of what function is actually called by the expression. One might imagine that NMODE finds defuns by moving upward a level of parentheses until there were no more levels to go up. This would require scanning all the way back to the beginning of the file. To speed up the operation, NMODE assumes that any "(" in column 0 is the start of a defun. This heuristic is nearly always right and avoids the costly scan. The commands to move to the beginning and end of the current defun are C-M-[ (203/move-backward-defun-command201/) and C-M-] (203/end-of-defun-command201/). Alternate names for these two commands are C-M-A for C-M-[ and C-M-E for C-M-]. The alternate names are easier to type on many non-Meta keyboards. 201/Page 20-6 NMODE Manual (Commands for Manipulating Defuns) If you wish to operate on the current defun, use C-M-H (203/mark-defun-command201/) which puts point at the beginning and mark at the end of the current or next defun. 202/20.6 Lisp Grinding 201/The best way to keep Lisp code properly indented ("ground") is to use NMODE to re-indent it when it is changed. NMODE has commands to indent properly either a single line, a specified number of lines, or all of the lines inside a single form. Tab In Lisp mode, re-indents line according to parenthesis depth. Linefeed Equivalent to Return followed by Tab. M-^ Join two lines, leaving one space between them if appropriate. C-M-Q Re-indent all the lines within one list. The basic indentation function is 203/lisp-tab-command201/, which gives the current line the correct indentation as determined from the previous lines' indentation and parenthesis structure. This function is placed on Tab in Lisp mode (Use Meta-Tab or C-Q Tab to insert a tab). If executed at the beginning of a line, it leaves point after the indentation; when given inside the text on the line, it leaves point fixed with respect to the characters around it. When entering a large amount of new code, use Linefeed (203/indent-new-line-command201/), which is equivalent to a Return followed by a Tab. In Lisp mode, a Linefeed creates or moves down onto a blank line, and then gives it the appropriate indentation. To join two lines together, use the Meta-^ or Control-Meta-^ command (203/delete-indentation-command201/), which is approximately the opposite of Linefeed. It deletes any spaces and tabs at the front of the current line, and then deletes the line separator before the line. A single space is then inserted, if NMODE thinks that one is needed there. Spaces are not needed before a close parenthesis, or after an open parenthesis. If you are dissatisfied about where Tab indents the second and later lines of an form, you can override it. If you alter the indentation of one of the lines yourself, then Tab will indent successive lines of the same list to be underneath it. This is the right thing for functions which Tab indents unaesthetically. When you wish to re-indent code which has been altered or moved to a different level in the list structure, you have several commands available. You can re-indent a specific number of lines by giving the ordinary indent command (Tab, in Lisp mode) an argument. This indents as many lines as you say and moves to the line following them. Thus, if you underestimate, you can repeat the process later. You can re-indent the contents of a single form by positioning point before the beginning of it and typing Control-Meta-Q (203/lisp-indent-sexpr201/). The line the form starts on is not re-indented; thus, only the relative indentation 201/NMODE Manual (Lisp Grinding) Page 20-7 with in the form, and not its position, is changed. To correct the position as well, type a Tab before the C-M-Q. Another way to specify the range to be re-indented is with point and mark. The command C-M-\ (203/lisp-indent-region-command201/) applies Tab to every line whose first character is between point and mark. In Lisp mode, this does a Lisp indent. The standard pattern of indentation is as follows: the second line of the expression is indented under the first argument, if that is on the same line as the beginning of the expression; otherwise, the second line is indented two spaces more than the entire expression. Each following line is indented under the previous line whose nesting depth is the same. 202/20.7 Lisp Language Interface 201/The following section contains many commands starting with "Lisp-". This prefix is equivalent to C-], but can sometimes be typed using a soft key. 202/20.7.1 Evaluation 201/NMODE contains a number of facilities to allow the user to use the underlying LISP language. In addition to editing and pretty-printing LISP expressions with the commands in the preceding sections, the user can execute the LISP expressions in the buffer. Lisp-D Execute the current Defun. Lisp-E Execute the form starting on this line. Lisp-Y Yanks the last output into current buffer. Lisp-D (203/execute-defun-command201/) causes the Lisp reader to read and evaluate the current defun. If there is no current defun, the Lisp reader will read a form starting at the current location. We arrange for output to be appended to the end of the output buffer. The mark is set at the current location in the input buffer, in case user wants to go back. Lisp-E (203/execute-form-command201/) causes the Lisp reader to read and evaluate a form starting at the beginning of the current line. We arrange for output to be appended to the end of the output buffer. The mark is set at the current location in the input buffer, in case user wants to go back. Lisp-Y (203/yank-last-output-command201/) copies the last piece of output from the output buffer back into the current buffer, allowing it to be added to some code or text within the current buffer. 202/20.7.2 Debugging 201/The commands of the last subsection allow one to use the underlying LISP, provided that no errors occur in the evaluation of expressions. The commands of this subsection allow recovery from errors in evaluations. When an error occurs, one enters a "break loop". This is indicated by the presence of more than one angle bracket on the lisp prompt at the right hand 201/Page 20-8 NMODE Manual (Debugging) side of the mode line under the output buffer. When one is in a break loop, one can still evaluate lisp expressions. Additional errors at this point will wrap additional break loops around the current one. Commands available in break loops include: Lisp-A Abort break loops. Lisp-Q Quit current break loop. Lisp-B Backtrace function calls. Lisp-C Continue execution. Lisp-R Retry expression. Lisp-? Help command Lisp-A (203/lisp-abort-command201/) will pop out of an arbitrarily deep break loop. Lisp-Q (203/lisp-quit-command201/) exits the current break loop. It only pops up one level, unlike abort. Lisp-B (203/lisp-backtrace-command201/) lists all the function calls on the stack. The most recently invoked function is listed first. It is a good way to see how the offending expression got generated. Unfortunately, many internal functions of Lisp and NMODE are shown, so the list may get somewhat cluttered. Lisp-C (203/lisp-continue-command201/) causes the expression last printed to be returned as the value of the offending expression. This allows a user to recover from a low level error in an involved calculation if they know what should have been returned by the offending expression. This is also often useful as an automatic stub: If an expression containing an undefined function is evaluated, a Break loop is entered, and this may be used to return the value of the function call. Lisp-R (203/lisp-retry-command201/) tries to evaluate the offending expression again, and to continue the computation. This is often useful after defining a missing function, or assigning a value to a variable. Lisp-? (203/lisp-help-command201/) lists the lisp commands available. When in a break loop it prints: "Lisp break commands: Q-quit;A-abort;R-retry;C-continue;B-backtrace" Otherwise it prints: "Lisp commands: E-execute form;Y-yank last output;L-invoke Lisp Listener"