digitalmars.D.learn - linear search using 'find' on an array of structs?
- captain_fid (28/28) Mar 08 2014 import std.container: find, equal, empty;
- captain_fid (32/60) Mar 08 2014 import std.container;
- Philippe Sigaud (25/34) Mar 09 2014 But clist is an array of c's, it has no `.name` field by itself. So, put
- captain_fid (4/54) Mar 10 2014 Thanks for the simple explanation Phillppe. Someone else
import std.container: find, equal, empty; import std.container : SList; struct c { int idx; string name; } c[] clist = [ {1, "name1"}, {2, "name2"}, { 3, "name3" } ]; // c* clist = [ {1, "name1"}, {2, "name2"}, { 3, "name3" } ]; int main() { // Case-insensitive find of a string string[] s = [ "Hello", "world", "!" ]; assert(!find!("toLower(a) == b")(s, "hello").empty); assert(!find!("toLower(a) == b")(clist.name, "name2").empty); return 0; } I went looking to replace several foreach statements. Can 'find' (in understand it's just a linear search) be used on an array of structures like above. Example pulled and modified. Above code gives me (naturally) - ... no property 'name' for type 'cp[]'. Interestingly, I had accidentally coded the commented out line before and it compiles correctly but will (as you guessed it) fail. Sorry for the basics...
Mar 08 2014
On Saturday, 8 March 2014 at 18:08:44 UTC, captain_fid wrote:import std.container: find, equal, empty; import std.container : SList; struct c { int idx; string name; } c[] clist = [ {1, "name1"}, {2, "name2"}, { 3, "name3" } ]; // c* clist = [ {1, "name1"}, {2, "name2"}, { 3, "name3" } ]; int main() { // Case-insensitive find of a string string[] s = [ "Hello", "world", "!" ]; assert(!find!("toLower(a) == b")(s, "hello").empty); assert(!find!("toLower(a) == b")(clist.name, "name2").empty); return 0; } I went looking to replace several foreach statements. Can 'find' (in understand it's just a linear search) be used on an array of structures like above. Example pulled and modified. Above code gives me (naturally) - ... no property 'name' for type 'cp[]'. Interestingly, I had accidentally coded the commented out line before and it compiles correctly but will (as you guessed it) fail. Sorry for the basics...import std.container; import std.algorithm; import std.array; import std.range; import std.stdio; struct C { int idx; string name; bool opEquals()(auto ref const C v) const { return v.idx == this.idx; } int opCmp(ref const C v) { return v.idx == this.idx; } } int main() { C[] d = [ {1, "name1"}, {2, "name2"}, { 3, "name3" } ]; auto r = assumeSorted(d); assert(r.canFind(C(3, ""))); assert(!r.canFind(C(32,""))); writeln( r.find(C(2, ""))); return 0; } // yields .... // [C(2, "name2"), C(3, "name3") ] Well, I see that both opEquals and opCmp needed to be overridden. But it's odd that C(3, "name3") is returned as well as C(2, "name2"). And the "" is ugly... Any suggestions would be helpful.
Mar 08 2014
assert(!find!("toLower(a) == b")(s, "hello").empty); assert(!find!("toLower(a) == b")(clist.name, "name2").empty);But clist is an array of c's, it has no `.name` field by itself. So, put the `.name` call inside the comparator: assert( find!("toLower(a.name) == b")(clist <http://clist.name/>*,* "name2").empty); This gives me this code: import std.algorithm: find; import std.array: empty; import std.uni: toLower; struct C // Use UpperCase for you user-defined types { int idx; string name; } C[] clist = [ {1, "name1"}, {2, "name2"}, { 3, "name3" } ]; void main() // no need to return 0 { auto target = clist.find!((a,b) => toLower(a.name) == b)("name2"); assert(!target.empty); } Using UFCS (Universal Function Call Syntax) to tranform f(a,b) into a.f(b). I used it on `find`.I went looking to replace several foreach statements. Can 'find' (in understand it's just a linear search) be used on an array of structures like above.Sure, as long as you tell it how you will get the info from the range (it defaults to simple equality).Example pulled and modified. Above code gives me (naturally) - ... no property 'name' for type 'cp[]'. Interestingly, I had accidentally coded the commented out line before and it compiles correctly but will (as you guessed it) fail.I never use pointers in D. I suppose the `.name` call is propagated to the array elements?
Mar 09 2014
On Sunday, 9 March 2014 at 10:46:26 UTC, Philippe Sigaud wrote:Thanks for the simple explanation Phillppe. Someone else mentioned before not using pointers in D (the loss of array goodness like mentioned in Andrei's book). Bad habits...assert(!find!("toLower(a) == b")(s, "hello").empty); assert(!find!("toLower(a) == b")(clist.name, "name2").empty);But clist is an array of c's, it has no `.name` field by itself. So, put the `.name` call inside the comparator: assert( find!("toLower(a.name) == b")(clist <http://clist.name/>*,* "name2").empty); This gives me this code: import std.algorithm: find; import std.array: empty; import std.uni: toLower; struct C // Use UpperCase for you user-defined types { int idx; string name; } C[] clist = [ {1, "name1"}, {2, "name2"}, { 3, "name3" } ]; void main() // no need to return 0 { auto target = clist.find!((a,b) => toLower(a.name) == b)("name2"); assert(!target.empty); } Using UFCS (Universal Function Call Syntax) to tranform f(a,b) into a.f(b). I used it on `find`.I went looking to replace several foreach statements. Can 'find' (in understand it's just a linear search) be used on an array of structures like above.Sure, as long as you tell it how you will get the info from the range (it defaults to simple equality).Example pulled and modified. Above code gives me (naturally) - ... no property 'name' for type 'cp[]'. Interestingly, I had accidentally coded the commented out line before and it compiles correctly but will (as you guessed it) fail.I never use pointers in D. I suppose the `.name` call is propagated to the array elements?
Mar 10 2014