Add Grep exercise

config.json

@@ -1377,6 +1377,17 @@
         "topics": [
           "strings"
         ]
+      },
+      {
+        "slug": "grep",
+        "name": "Grep",
+        "uuid": "4592877f-5b1e-4c8f-89aa-9e206de696eb",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5,
+        "topics": [
+          "strings"
+        ]
       }
     ],
     "foregone": [

exercises/practice/grep/.docs/instructions.append.md

@@ -0,0 +1,4 @@
+# Hints
+
+To simplify the exercise the flags are already given parsed and input files read,
+therefore no IO operations and argument parsing need to be performed.

exercises/practice/grep/.docs/instructions.md

@@ -0,0 +1,27 @@
+# Instructions
+
+Search files for lines matching a search string and return all matching lines.
+
+The Unix [`grep`][grep] command searches files for lines that match a regular expression.
+Your task is to implement a simplified `grep` command, which supports searching for fixed strings.
+
+The `grep` command takes three arguments:
+
+1. The string to search for.
+2. Zero or more flags for customizing the command's behavior.
+3. One or more files to search in.
+
+It then reads the contents of the specified files (in the order specified), finds the lines that contain the search string, and finally returns those lines in the order in which they were found.
+When searching in multiple files, each matching line is prepended by the file name and a colon (':').
+
+## Flags
+
+The `grep` command supports the following flags:
+
+- `-n` Prepend the line number and a colon (':') to each line in the output, placing the number after the filename (if present).
+- `-l` Output only the names of the files that contain at least one matching line.
+- `-i` Match using a case-insensitive comparison.
+- `-v` Invert the program -- collect all lines that fail to match.
+- `-x` Search only for lines where the search string matches the entire line.
+
+[grep]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/grep.html

exercises/practice/grep/.meta/config.json

@@ -0,0 +1,23 @@
+{
+  "authors": [
+    "tofische"
+  ],
+  "files": {
+    "solution": [
+      "src/Grep.hs",
+      "package.yaml"
+    ],
+    "test": [
+      "test/Tests.hs"
+    ],
+    "example": [
+      ".meta/examples/success-standard/src/Grep.hs"
+    ],
+    "invalidator": [
+      "stack.yaml"
+    ]
+  },
+  "blurb": "Search a file for lines matching a regular expression pattern. Return the line number and contents of each matching line.",
+  "source": "Conversation with Nate Foster.",
+  "source_url": "https://www.cs.cornell.edu/Courses/cs3110/2014sp/hw/0/ps0.pdf"
+}

exercises/practice/grep/.meta/examples/success-standard/package.yaml

@@ -0,0 +1,16 @@
+name: grep
+
+dependencies:
+  - base
+
+library:
+  exposed-modules: Grep
+  source-dirs: src
+
+tests:
+  test:
+    main: Tests.hs
+    source-dirs: test
+    dependencies:
+      - grep
+      - hspec

exercises/practice/grep/.meta/examples/success-standard/src/Grep.hs

@@ -0,0 +1,33 @@
+module Grep (grep, Flag(..)) where
+
+import Data.Char (toLower)
+import Data.List (isInfixOf)
+
+data Flag = N | L | I | V | X deriving (Eq, Ord)
+
+type Flags = [Flag]
+type File = (String, [String])
+type Files = [File]
+
+grep :: String -> Flags -> Files -> [String]
+grep pattern flags files = concatMap grepInFile files
+    where
+        flagN = N `elem` flags
+        flagL = L `elem` flags
+        flagI = I `elem` flags
+        flagV = V `elem` flags
+        flagX = X `elem` flags
+        pattern' = if flagI then map toLower pattern else pattern
+        multiple = length files > 1
+        grepInFile (fileName, content) = if flagL && not (null matchInFile) then [fileName] else matchInFile
+            where
+                matchInFile = concatMap grepInLine $ zip content [1..]
+                grepInLine :: (String, Int) -> [String]
+                grepInLine (line, lineNum) = [res | if flagV then not match else match]
+                    where
+                        line' = if flagI then map toLower line else line
+                        match = if flagX then pattern' == line' else pattern' `isInfixOf` line'
+                        res =
+                            (if multiple then fileName <> ":" else "") <>
+                            (if flagN then show lineNum <> ":" else "") <>
+                            line

exercises/practice/grep/.meta/tests.toml

@@ -0,0 +1,85 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[9049fdfd-53a7-4480-a390-375203837d09]
+description = "Test grepping a single file -> One file, one match, no flags"
+
+[76519cce-98e3-46cd-b287-aac31b1d77d6]
+description = "Test grepping a single file -> One file, one match, print line numbers flag"
+
+[af0b6d3c-e0e8-475e-a112-c0fc10a1eb30]
+description = "Test grepping a single file -> One file, one match, case-insensitive flag"
+
+[ff7af839-d1b8-4856-a53e-99283579b672]
+description = "Test grepping a single file -> One file, one match, print file names flag"
+
+[8625238a-720c-4a16-81f2-924ec8e222cb]
+description = "Test grepping a single file -> One file, one match, match entire lines flag"
+
+[2a6266b3-a60f-475c-a5f5-f5008a717d3e]
+description = "Test grepping a single file -> One file, one match, multiple flags"
+
+[842222da-32e8-4646-89df-0d38220f77a1]
+description = "Test grepping a single file -> One file, several matches, no flags"
+
+[4d84f45f-a1d8-4c2e-a00e-0b292233828c]
+description = "Test grepping a single file -> One file, several matches, print line numbers flag"
+
+[0a483b66-315b-45f5-bc85-3ce353a22539]
+description = "Test grepping a single file -> One file, several matches, match entire lines flag"
+
+[3d2ca86a-edd7-494c-8938-8eeed1c61cfa]
+description = "Test grepping a single file -> One file, several matches, case-insensitive flag"
+
+[1f52001f-f224-4521-9456-11120cad4432]
+description = "Test grepping a single file -> One file, several matches, inverted flag"
+
+[7a6ede7f-7dd5-4364-8bf8-0697c53a09fe]
+description = "Test grepping a single file -> One file, no matches, various flags"
+
+[3d3dfc23-8f2a-4e34-abd6-7b7d140291dc]
+description = "Test grepping a single file -> One file, one match, file flag takes precedence over line flag"
+
+[87b21b24-b788-4d6e-a68b-7afe9ca141fe]
+description = "Test grepping a single file -> One file, several matches, inverted and match entire lines flags"
+
+[ba496a23-6149-41c6-a027-28064ed533e5]
+description = "Test grepping multiples files at once -> Multiple files, one match, no flags"
+
+[4539bd36-6daa-4bc3-8e45-051f69f5aa95]
+description = "Test grepping multiples files at once -> Multiple files, several matches, no flags"
+
+[9fb4cc67-78e2-4761-8e6b-a4b57aba1938]
+description = "Test grepping multiples files at once -> Multiple files, several matches, print line numbers flag"
+
+[aeee1ef3-93c7-4cd5-af10-876f8c9ccc73]
+description = "Test grepping multiples files at once -> Multiple files, one match, print file names flag"
+
+[d69f3606-7d15-4ddf-89ae-01df198e6b6c]
+description = "Test grepping multiples files at once -> Multiple files, several matches, case-insensitive flag"
+
+[82ef739d-6701-4086-b911-007d1a3deb21]
+description = "Test grepping multiples files at once -> Multiple files, several matches, inverted flag"
+
+[77b2eb07-2921-4ea0-8971-7636b44f5d29]
+description = "Test grepping multiples files at once -> Multiple files, one match, match entire lines flag"
+
+[e53a2842-55bb-4078-9bb5-04ac38929989]
+description = "Test grepping multiples files at once -> Multiple files, one match, multiple flags"
+
+[9c4f7f9a-a555-4e32-bb06-4b8f8869b2cb]
+description = "Test grepping multiples files at once -> Multiple files, no matches, various flags"
+
+[ba5a540d-bffd-481b-bd0c-d9a30f225e01]
+description = "Test grepping multiples files at once -> Multiple files, several matches, file flag takes precedence over line number flag"
+
+[ff406330-2f0b-4b17-9ee4-4b71c31dd6d2]
+description = "Test grepping multiples files at once -> Multiple files, several matches, inverted and match entire lines flags"

exercises/practice/grep/package.yaml

@@ -0,0 +1,21 @@
+name: grep
+version: 1.0.0.0
+
+dependencies:
+  - base
+
+library:
+  exposed-modules: Grep
+  source-dirs: src
+  ghc-options: -Wall
+  # dependencies:
+  # - foo       # List here the packages you
+  # - bar       # want to use in your solution.
+
+tests:
+  test:
+    main: Tests.hs
+    source-dirs: test
+    dependencies:
+      - grep
+      - hspec

exercises/practice/grep/src/Grep.hs

@@ -0,0 +1,10 @@
+module Grep (grep, Flag(..)) where
+
+data Flag = N | L | I | V | X deriving (Eq, Ord)
+
+type Flags = [Flag]
+type File = (String, [String])
+type Files = [File]
+
+grep :: String -> Flags -> Files -> [String]
+grep pattern flags files = error "You need to implement this function."

exercises/practice/grep/stack.yaml

@@ -0,0 +1 @@
+resolver: lts-20.18