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expressions.y
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expressions.y
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%{
package expressions
import (
"fmt"
"github.com/osteele/liquid/values"
)
func init() {
// This allows adding and removing references to fmt in the rules below,
// without having to comment and un-comment the import statement above.
_ = ""
}
%}
%union {
name string
val interface{}
f func(Context) values.Value
s string
ss []string
exprs []Expression
cycle Cycle
cyclefn func(string) Cycle
loop Loop
loopmods loopModifiers
filter_params []valueFn
}
%type<f> expr rel filtered cond
%type<filter_params> filter_params
%type<exprs> exprs expr2
%type<cycle> cycle
%type<cyclefn> cycle2
%type<ss> cycle3
%type<loop> loop
%type<loopmods> loop_modifiers
%type<s> string
%token <val> LITERAL
%token <name> IDENTIFIER KEYWORD PROPERTY
%token ASSIGN CYCLE LOOP WHEN
%token EQ NEQ GE LE IN AND OR CONTAINS DOTDOT
%left '.' '|'
%left '<' '>'
%%
start:
cond ';' { yylex.(*lexer).val = $1 }
| ASSIGN IDENTIFIER '=' filtered ';' {
yylex.(*lexer).Assignment = Assignment{$2, &expression{$4}}
}
| CYCLE cycle ';' { yylex.(*lexer).Cycle = $2 }
| LOOP loop ';' { yylex.(*lexer).Loop = $2 }
| WHEN exprs ';' { yylex.(*lexer).When = When{$2} }
;
cycle: string cycle2 { $$ = $2($1) };
cycle2:
':' string cycle3 {
h, t := $2, $3
$$ = func(g string) Cycle { return Cycle{g, append([]string{h}, t...)} }
}
| cycle3 {
vals := $1
$$ = func(h string) Cycle { return Cycle{Values: append([]string{h}, vals...)} }
}
;
cycle3:
/* empty */ { $$ = []string{} }
| ',' string cycle3 { $$ = append([]string{$2}, $3...) }
;
exprs: expr expr2 { $$ = append([]Expression{&expression{$1}}, $2...) } ;
expr2:
/* empty */ { $$ = []Expression{} }
| ',' expr expr2 { $$ = append([]Expression{&expression{$2}}, $3...) }
;
string: LITERAL {
s, ok := $1.(string)
if !ok {
panic(SyntaxError(fmt.Sprintf("expected a string for %q", $1)))
}
$$ = s
};
loop: IDENTIFIER IN filtered loop_modifiers {
name, expr, mods := $1, $3, $4
$$ = Loop{name, &expression{expr}, mods}
}
;
loop_modifiers: /* empty */ { $$ = loopModifiers{} }
| loop_modifiers IDENTIFIER {
switch $2 {
case "reversed":
$1.Reversed = true
default:
panic(SyntaxError(fmt.Sprintf("undefined loop modifier %q", $2)))
}
$$ = $1
}
| loop_modifiers KEYWORD expr {
switch $2 {
case "cols":
$1.Cols = &expression{$3}
case "limit":
$1.Limit = &expression{$3}
case "offset":
$1.Offset = &expression{$3}
default:
panic(SyntaxError(fmt.Sprintf("undefined loop modifier %q", $2)))
}
$$ = $1
}
;
expr:
LITERAL { val := $1; $$ = func(Context) values.Value { return values.ValueOf(val) } }
| IDENTIFIER { name := $1; $$ = func(ctx Context) values.Value { return values.ValueOf(ctx.Get(name)) } }
| expr PROPERTY { $$ = makeObjectPropertyExpr($1, $2) }
| expr '[' expr ']' { $$ = makeIndexExpr($1, $3) }
| '(' expr DOTDOT expr ')' { $$ = makeRangeExpr($2, $4) }
| '(' cond ')' { $$ = $2 }
;
filtered:
expr
| filtered '|' IDENTIFIER { $$ = makeFilter($1, $3, nil) }
| filtered '|' KEYWORD filter_params { $$ = makeFilter($1, $3, $4) }
;
filter_params:
expr { $$ = []valueFn{$1} }
| filter_params ',' expr
{ $$ = append($1, $3) }
rel:
filtered
| expr EQ expr {
fa, fb := $1, $3
$$ = func(ctx Context) values.Value {
a, b := fa(ctx), fb(ctx)
return values.ValueOf(a.Equal(b))
}
}
| expr NEQ expr {
fa, fb := $1, $3
$$ = func(ctx Context) values.Value {
a, b := fa(ctx), fb(ctx)
return values.ValueOf(!a.Equal(b))
}
}
| expr '>' expr {
fa, fb := $1, $3
$$ = func(ctx Context) values.Value {
a, b := fa(ctx), fb(ctx)
return values.ValueOf(b.Less(a))
}
}
| expr '<' expr {
fa, fb := $1, $3
$$ = func(ctx Context) values.Value {
a, b := fa(ctx), fb(ctx)
return values.ValueOf(a.Less(b))
}
}
| expr GE expr {
fa, fb := $1, $3
$$ = func(ctx Context) values.Value {
a, b := fa(ctx), fb(ctx)
return values.ValueOf(b.Less(a) || a.Equal(b))
}
}
| expr LE expr {
fa, fb := $1, $3
$$ = func(ctx Context) values.Value {
a, b := fa(ctx), fb(ctx)
return values.ValueOf(a.Less(b) || a.Equal(b))
}
}
| expr CONTAINS expr { $$ = makeContainsExpr($1, $3) }
;
cond:
rel
| cond AND rel {
fa, fb := $1, $3
$$ = func(ctx Context) values.Value {
return values.ValueOf(fa(ctx).Test() && fb(ctx).Test())
}
}
| cond OR rel {
fa, fb := $1, $3
$$ = func(ctx Context) values.Value {
return values.ValueOf(fa(ctx).Test() || fb(ctx).Test())
}
}
;