From 9d69f8a518c16adeeaa8e88d2a84e185716eb2f4 Mon Sep 17 00:00:00 2001 From: matt venn <matt@mattvenn.net> Date: Wed, 22 Apr 2020 17:54:39 +0200 Subject: [PATCH 1/2] change order of statements and make gender neutral --- docs/examples/puzzles/wolf_goat_cabbage.sv | 33 +++++++++++----------- 1 file changed, 17 insertions(+), 16 deletions(-) diff --git a/docs/examples/puzzles/wolf_goat_cabbage.sv b/docs/examples/puzzles/wolf_goat_cabbage.sv index 9c9fe7a..6821098 100644 --- a/docs/examples/puzzles/wolf_goat_cabbage.sv +++ b/docs/examples/puzzles/wolf_goat_cabbage.sv @@ -1,38 +1,39 @@ -// A man needs to cross a river with a wolf, a goat and a cabbage. His boat is only large -// enough to carry himself and one of his three possessions, so he must transport these -// items one at a time. However, if he leaves the wolf and the goat together unattended, -// then the wolf will eat the goat; similarly, if he leaves the goat and the cabbage together -// unattended, then the goat will eat the cabbage. How can the man get across safely with -// his three items? +// A person needs to cross a river with a wolf, a goat and a cabbage. Their boat is only large +// enough to carry themselves and one of their three possessions, so they must transport these +// items one at a time. However, if they leave the wolf and the goat together unattended, +// then the wolf will eat the goat; similarly, if they leave the goat and the cabbage together +// unattended, then the goat will eat the cabbage. How can the person get across safely with +// their three items? module wolf_goat_cabbage (input clk, input w, g, c); // everyone starts at the 1st river bank reg bank_w = 0; // wolf reg bank_g = 0; // goat reg bank_c = 0; // cabbage - reg bank_m = 0; // man + reg bank_person = 0; // person who drives the boat always @(posedge clk) begin + // person travels and takes the selected item with him + if (w && (bank_w == bank_person)) bank_w <= !bank_person; + if (g && (bank_g == bank_person)) bank_g <= !bank_person; + if (c && (bank_c == bank_person)) bank_c <= !bank_person; + bank_person <= !bank_person; + // maximum one of the control signals must be high assume (w+g+c <= 1); // we want wolf, goat, and cabbage on the 2nd river bank - cover (bank_w && bank_g && bank_c); + // write a cover statement that will result in the desired combination + cover(bank_w == 1 && bank_g == 1 && bank_c == 1); // don't leave wolf and goat unattended - if (bank_w != bank_m) begin + if (bank_w != bank_person) begin assume (bank_w != bank_g); end // don't leave goat and cabbage unattended - if (bank_g != bank_m) begin + if (bank_g != bank_person) begin assume (bank_g != bank_c); end - - // man travels and takes the selected item with him - if (w && (bank_w == bank_m)) bank_w <= !bank_m; - if (g && (bank_g == bank_m)) bank_g <= !bank_m; - if (c && (bank_c == bank_m)) bank_c <= !bank_m; - bank_m <= !bank_m; end endmodule From 68127a37062d98b9c4fb0074ec950b4e767b153b Mon Sep 17 00:00:00 2001 From: matt venn <matt@mattvenn.net> Date: Wed, 22 Apr 2020 19:11:23 +0200 Subject: [PATCH 2/2] consistent naming and put person moving line at the top --- docs/examples/puzzles/wolf_goat_cabbage.sv | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/docs/examples/puzzles/wolf_goat_cabbage.sv b/docs/examples/puzzles/wolf_goat_cabbage.sv index 6821098..4c034cf 100644 --- a/docs/examples/puzzles/wolf_goat_cabbage.sv +++ b/docs/examples/puzzles/wolf_goat_cabbage.sv @@ -10,29 +10,28 @@ module wolf_goat_cabbage (input clk, input w, g, c); reg bank_w = 0; // wolf reg bank_g = 0; // goat reg bank_c = 0; // cabbage - reg bank_person = 0; // person who drives the boat + reg bank_p = 0; // person who drives the boat always @(posedge clk) begin // person travels and takes the selected item with him - if (w && (bank_w == bank_person)) bank_w <= !bank_person; - if (g && (bank_g == bank_person)) bank_g <= !bank_person; - if (c && (bank_c == bank_person)) bank_c <= !bank_person; - bank_person <= !bank_person; + bank_p <= !bank_p; + if (w && (bank_w == bank_p)) bank_w <= !bank_p; + if (g && (bank_g == bank_p)) bank_g <= !bank_p; + if (c && (bank_c == bank_p)) bank_c <= !bank_p; // maximum one of the control signals must be high assume (w+g+c <= 1); // we want wolf, goat, and cabbage on the 2nd river bank - // write a cover statement that will result in the desired combination cover(bank_w == 1 && bank_g == 1 && bank_c == 1); // don't leave wolf and goat unattended - if (bank_w != bank_person) begin + if (bank_w != bank_p) begin assume (bank_w != bank_g); end // don't leave goat and cabbage unattended - if (bank_g != bank_person) begin + if (bank_g != bank_p) begin assume (bank_g != bank_c); end end