diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 41 |
1 files changed, 35 insertions, 6 deletions
@@ -7650,7 +7650,7 @@ Repeat supports arguments. .cblk .mets @(repeat .mets \ \ \ [:counter >> { symbol | >> ( symbol << expr )}] -.mets \ \ \ [:vars <> ( symbol *)]) +.mets \ \ \ [:vars >> ({ symbol | >> ( symbol << expr )}*)]) .cble The @@ -7661,7 +7661,7 @@ access to the repetition count, starting at zero, incrementing with each repetition. If the the argument is given as .cblk .meti >> ( symbol << expr ) -.cblk +.cble then .meta expr is a Lisp expression whose value is taken as a displacement value which @@ -7673,10 +7673,20 @@ which counts from 1. The .code :vars -argument specifies a list of variables. The repeat directive -will pick out from this list those variables which have bindings. -It will assume that all these variables occur in the repeat block and -are to be iterated. This syntax is needed for situations in which +argument specifies a list of variable names, or pairs consisting of a variable +name and Lisp expression. For every variable paired with a Lisp expression, +the expression is evaluated, and a binding is introduced, associating +that variable with the expression's value. + +The repeat directive then processes the list of variables, selecting from it +those which have a binding, either a previously existing binding or one just +introduced from a Lisp expression. For each selected variable, repeat +will assume that the variable occur in the repeat block and contains +a list to be iterated. + +Thus +.code :vars +Firstly, it is needed for situations in which .code @(repeat) is not able to deduce the existence of a variable in the block. It does not dig very deeply to discover variables, and does not "see" @@ -7715,6 +7725,25 @@ Now the repeat block iterates over list and the output is: <c> .cble +Secondly, The variable binding syntax supported by +.code :vars +additionally provides a solution for situations when it is necessary to iterate +over some list, but that list is the result of an expression, and not stored in +any variable. A repeat block iterates only over lists emanating from variables; +it does not iterate over lists pulled from arbitrary expressions. + +Example: output all file names matching the +.code *.txr +pattern in the current directory: + +.cblk + @(output) + @(repeat :vars (name (glob "*.txr"))) + @name + @(end) + @(end) +.cble + .coNP Nested @ repeat directives If a |