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expressions.y
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expressions.y
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%{
package expressions
import (
"fmt"
"math"
"github.com/massdriver-cloud/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 int_or_var loop_expr
%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)))
}
$$ = s
};
loop: IDENTIFIER IN loop_expr loop_modifiers {
name, expr, mods := $1, $3, $4
$$ = Loop{name, &expression{expr}, mods}
}
;
loop_expr : '(' int_or_var DOTDOT int_or_var ')' {
$$ = makeRangeExpr($2, $4)
}
| filtered
;
// TODO DRY w/ expr
int_or_var:
LITERAL { val := $1; $$ = func(Context) values.Value { return values.ValueOf(val) } }
| IDENTIFIER { name := $1; $$ = func(ctx Context) values.Value { return values.ValueOf(ctx.Get(name)) } }
;
loop_modifiers: /* empty */ { $$ = loopModifiers{Cols: math.MaxInt32} }
| loop_modifiers IDENTIFIER {
switch $2 {
case "reversed":
$1.Reversed = true
default:
panic(SyntaxError(fmt.Sprintf("undefined loop modifier %q", $2)))
}
$$ = $1
}
| loop_modifiers KEYWORD LITERAL { // TODO can this be a variable?
switch $2 {
case "cols":
cols, ok := $3.(int)
if !ok {
panic(SyntaxError(fmt.Sprintf("loop cols must an integer")))
}
$1.Cols = cols
case "limit":
limit, ok := $3.(int)
if !ok {
panic(SyntaxError(fmt.Sprintf("loop limit must an integer")))
}
$1.Limit = &limit
case "offset":
offset, ok := $3.(int)
if !ok {
panic(SyntaxError(fmt.Sprintf("loop offset must an integer")))
}
$1.Offset = offset
default:
panic(SyntaxError(fmt.Sprintf("undefined loop modifier %q", $2)))
}
$$ = $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) }
| '(' 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())
}
}
;