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DOCS: update the grammar and expression docs.

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Adds the new form of format expressions using tuples.

Regarding Issue #23
This commit is contained in:
Jeremy Wall 2019-01-28 21:29:31 -06:00
parent 3c1b3ce86a
commit 315fbabc3d
2 changed files with 22 additions and 3 deletions
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21
docsite/site/content/reference/expressions.md
View File

@ -258,8 +258,9 @@ let imported_val = (import "some_file.ucg").val;
Format Expressions
----------
UCG has a format expression that has a limited form of string templating. A
format expression starts with a string followed by the `%` operator and a list
UCG has a format expression that has a limited form of string templating. Format expressions come in two forms.
The simplest form starts with a string followed by the `%` operator and a list
of arguments in parentheses separated by commas. Trailing commas are allowed.
The format string should have `@` characters in each location where a value
should be placed. Any primitive value can be used as an argument.
@ -268,6 +269,22 @@ should be placed. Any primitive value can be used as an argument.
"https://@:@/" % (host, port)
```
A slightly more complex form starts with a string followed by the `%` operator and
an expression. the template string can then reference the result of the expression
in expressions embedded within the format string. The expressions result can be referenced using the special name `item` in the embedded expression. The result
of the expression will be rendered as the default string representation in the
resulting string.
```
let tpl = {
foo = {
bar = [0, 1, 2],
},
};
"foo.bar.1 == @{item.foo.bar.1}" % tpl;
```
Range Expression
----------------

4
docsite/site/content/reference/grammar.md
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@ -132,7 +132,9 @@ call_expr: bareword, lparen, [arglist], rparen ;
#### Format Expression
```
format_expr: str, percent, lparen, [arglist], rparen ;
format_arg_list: lparen, [arglist], rparen ;
foramt_expr_arg: expression ;
format_expr: str, percent, (format_arg_list | format_expr_arg) ;
```
### Functional processing expressions