Happy is a YACC-like parse generator for Haskell
Happy is a yacc like parse generator for the haskell programming language.
Questions tagged [happy]
108 questions
1
vote
1 answer
Haskell, No instance for (Show ([String, Int)] -> Int
Trying to compile Haskell.Happy example here: http://www.haskell.org/happy/doc/html/sec-using.html#sec-other-datatypes, after generating .hs file with happy, I'm getting the
No instance for (Show ([String, Int)] -> Int
error, trying to compile it,…
Herokiller
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1
vote
1 answer
Alex, Happy, Cabal, and Re-preprocessing
I am using Alex 3.0.5, Happy 1.18.10, Cabal 1.16.0.2
I have a small compiler project that is built using Cabal. I am exposing the compiler's internals as a library, so I have in the exposed modules section, MyLangLex and MyLangPar. If I delete the…
Jonathan Gallagher
- 2,115
- 2
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1
vote
1 answer
Haskell - Happy - "No instance ..." error
I'm trying to get familiar with Happy parser generator for Haskell. Currently, I have an example from the documentation but when I compile the program, I get an error.
This is the code:
{
module Main where
import Data.Char
}
%name calc
%tokentype {…
John Smith
- 1,276
- 4
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1
vote
1 answer
Reduce/Reduce conflict when introducing pointers in my grammar
I'm working on a small compiler in order to get a greater appreciation of the difficulties of creating one's own language. Right now I'm at the stage of adding pointer functionality to my grammar but I got a reduce/reduce conflict by doing it.
Here…
Tarrasch
- 10,199
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1
vote
2 answers
haskell happy - "Couldn't match expected type"
I have some problems to understand error messages of the parser generator system happy for haskell.
For instance this code
{
module Test_parser where
import System.IO
import Test_lexer
}
%name parse
%tokentype { Token }
%error { parseError…
jimmyt
- 491
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- 10
0
votes
1 answer
LEETCODE 202 HAPPY NUMBER (PYTHON)
class Solution:
def isHappy(self, n: int) -> bool:
visit = set()
def happy(n):
temp = n
n = 0
for i in str(temp):
n += int(i)**2
if n == 1:
return…
0
votes
1 answer
How can i get a false value if the inputted number isn't a happy one?
*hi there here is my answer for this challenge :
Write an algorithm to determine if a number n is "happy".
A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares…
Fayçal Hamdi
- 11
- 1
0
votes
1 answer
Parsing switch statements with Happy
So, I'm trying to parse code containg switch statements like this
function (a : Boolean) equals (b : Boolean) : Boolean {
switch (a) {
case true:
switch (b) {
case true:
…
Anthony
- 410
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0
votes
1 answer
Optional prefix in LBNF/BNFC grammar without shift/reduce conflicts
I am trying to write a LBNF/BNFC grammar for a C-like language. In C there are many possible modifiers that you may or may not write in front of a declaration (like inline, const, volatile and so on).
I am trying to write my grammar to reuse code…
Grisu47
- 530
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- 16
0
votes
1 answer
Happy/YACC reducing when it should shift
I'm working on a parser and I'm really frustrated. In the language, we can have an expression like:
new int[3][][]
or
new int[3]
Most of it parses correctly, except for the empty arrays at the end.
In my parser I have:
Expression : int
…
Kevin Burke
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0
votes
1 answer
Resolve conflict in bison grammar with space separated expression lists + if/then/else
I have the following yacc/bison/happy grammar:
%token
if TokenIf
then TokenThen
else TokenElse
true TokenTrue
false TokenFalse
%left APP
%right IF
%%
Hungry
: NoHungry
|…
Sebastian Graf
- 3,602
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0
votes
0 answers
Cabal Build Producing Errors - Code Seems Fine Manually?
Throughout my development i've been manually running alex/happy to generate my parser files and then running ghci to test the code. This works fine and loads me into GHCI, but whenever I run cabal repl the program throws an error in my Parser.hs…
Sheldor
- 11
- 4
0
votes
0 answers
Does happy allow single-line comments?
Is there a way to comment everything to the end of the line, like -- in Haskell? The only comment syntax I could find was the {- commented stuff -} syntax.
sid-kap
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0
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1 answer
Happy Parse Error
I'm currently using the alex and happy lexer/parser generators to implement a parser for the Ethereum Smart contract language solidity. Currently I'm using a reduced grammar in order to simplify the initial development.
I'm running into an error…
Sheldor
- 11
- 4
0
votes
0 answers
Generating "expected" style error messages from Happy
As Happy generates a state machine and runs through it upon parsing, I presume when hitting a parse error it will be able to tell what tokens it was expecting.
Is there anyway to get this information as part of printing the error? Currently I'm just…
Clinton
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