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Diffstat (limited to 'doc/sciteco.7.template')
| -rw-r--r-- | doc/sciteco.7.template | 35 |
1 files changed, 27 insertions, 8 deletions
diff --git a/doc/sciteco.7.template b/doc/sciteco.7.template index 340f58b..42d1425 100644 --- a/doc/sciteco.7.template +++ b/doc/sciteco.7.template @@ -1004,8 +1004,8 @@ They correspond to structured IF-THEN-ELSE statements in other imperative languages. The general syntax of conditionals is as follows: .br -\# n"c if [| else ]' -\fIn\fB"\fIc if \fR[\fB|\fI else \fR] \fB'\fR +\# [n]"c if [| else ]' +[\fIn\fP]\fB"\fIc if \fR[\fB|\fI else \fR] \fB'\fR .br Whereas \fIn\fP is a value on the stack to test, \fIc\fP is a case-insignificant character identifying a @@ -1013,12 +1013,31 @@ condition to check for, \fIif\fP is a code block to execute if the condition applies and \fIelse\fP is an optional code block to execute if the condition does not apply. -The first command in the \fIif\fP block will not see -any arguments on the expression stack but values accumulated -on the expression stack by the \fIif\fP or \fIelse\fP blocks -are not discarded by the terminating single-quote. -In other words, conditionals may return values. -The possible conditions are defined in the following list: +The conditional pops at most one argument from the expression +stack \(em the remaining arguments may be evaluated by the +\fIif\fP or \fIelse\fP blocks. +Values accumulated on the expression stack by the \fIif\fP or \fIelse\fP +blocks are not discarded by the terminating single-quote. +In other words, conditionals may also return values. +The possible conditions are defined in the following list. +Unless \fIn\fP is defined optional, the conditionals described +below yield an error if \fIn\fP is omitted: +.TP +\# [n]"~ +[\fIn\fP]\fB\(dq~\fP +Applies if \fIn\fP is \fBnot\fP given (i.e. the argument +stack is empty). +If \fIn\fP is given (i.e. the stack is not empty), it is \fBnot\fP +removed from the expression stack. +This construct is especially useful in macros to imply default +parameter values. +For instance the following macro inserts \fIn\fP tab characters +(one by default): +.EX +@^Ut{ + "~1'<@^I//> +} +.EE .TP .IB n \(dqA Applies if \fIn\fP is the code of an alphabetic character. |